Enabling multiple computer systems to work effectively in sharing information and resources accounts for a substantial proportion (possibly 80%) of current work in the integration of computer systems. For example, a system in a retail bank may hold information relating to a customer's account, while quite a different system (such as a telephone switch) may hold more transient information regarding the source of origin of a customer's call. Making these separate systems work together (so as, say, to display the customer's account details on a screen using the telephone caller line ID as a key) presently involves using hardware and software to program each participating system to communicate specifically and directly with each other to achieve the desired result. The problem with this approach is that the complexity of the integration rises rapidly as the number of systems to be integrated increases. Furthermore, the specific programming skills required may become difficult to acquire and retain as individual integrated systems become older or even obsolete.
Attempts to address these problems have led to the development of “Information Brokers” or “Message Oriented Middleware” which enable one system to connect to another, often via an intermediary hub. This offers a considerable improvement because each integrated system requires only to be connected to the hub rather than to each of the other systems involved in the integration. Furthermore, the complexities of ensuring that messages arrive in the correct order at the recipient system, the queuing of messages so that temporary unavailability does not affect the overall integration, and the distribution of messages to multiple “subscribing” systems can all be handled within the message oriented middleware. An example of an existing message queuing system is described in U.S. Pat. No. 4,333,144 entitled “Task communicator for multiple computer system”.
One central problem with this approach, however, is that each system, being an “end point” in the integration, needs to be specifically programmed in the light of the operations to be done preceding and subsequent to the transmission of each message or batch of messages between systems. These operations have to be programmed in the light of and with knowledge of the equivalent operations of other integrated end points. As the number of integrated systems increases, this work becomes overwhelmingly complex. Automatic integration—that is, enabling systems of all kinds to work together without the need to explicitly program or re-program each system in every new case is not facilitated in this environment.